The present invention relates to an improved refractory closure plate for use as a movable plate in a sliding closure unit and to an improved sliding closure unit employing such closure plate. More particularly, the present invention is directed to such improved closure plate for use in a sliding closure unit of the type including at least one stationary plate having therethrough a discharge opening, the movable plate being mounted in sliding contact with the stationary plate, the movable plate having therethrough first and second discharge openings and including a closing area, and means for moving the movable plate between a closed position, whereat the closing area covers the discharge opening of the stationary plate, and alternate open positions, whereat one or the other of the discharge openings of the movable plate is aligned with the discharge opening of the stationary plate.
This type of sliding closure unit is employed for discharging a molten material from a vessel, particularly for discharging a molten metal from a metallurgical vessel. This type of sliding closure unit, including two or even more discharge openings in the movable closure plate, is employed to achieve relatively long pouring times without the need for changing the closure plates. This is possible with this type of sliding closure unit, since when one of the discharge openings has been worn to an extent to no longer be usable, it is possible to switch to another, still unused discharge opening of the movable closure plate. The discharge openings of the movable closure plate may have the same or different diameters.
A sliding closure unit including a single stationary refractory closure plate and a movable refractory closure plate is disclosed in West German Pat. No. 2,850,183. This structure, as well as all other known structures of sliding closure units, includes a housing having mounted therein a sliding frame operated by a first hydraulic cylinder drive. This sliding frame carries both a swivel frame and a second hydraulic cylinder drive connected therewith. The movable closure plate is held in the swivel frame. The sliding closure unit is operated, i.e. closed, opened or throttled, by the first drive by sliding the sliding frame together with the swivel frame, whereas the second drive is operated to switch from one discharge opening to another discharge opening by pivoting the swivel frame with respect to the sliding frame. During this operation, as during the movement of the sliding frame, the friction of the closure plates, which are locked in place in relation to each other and to other parts of the unit, must be overcome.
It is very expensive both to construct and to operate this known type of sliding closure unit. Both hydraulic drives require appropriate feed lines and independent controls. Furthermore, during the operation of switching between the discharge openings of the movable plate a heavy mass must be moved, i.e. the sliding frame together with the swivel frame and second drive.